A new species of Blastulospongia Pickett and Jell, 1983 from the middle Cambrian Devoncourt Limestone, Georgina Basin, Australia exhibits distinct perforation patterns characteristic of sphinctozoans. Recognition as a sphinctozoan-grade sponge confirms the poriferan affinity of this enigmatic genus, which appeared prior to the development of other hypercalcified sponge forms of chaetetids and stromatoporoids. Blastulospongia bouliaensis new species occurs together with four species of primitive spicular radiolarians: Echidnina irregularis Won in Won and Iams, 2002, Parechidnina aspinosa Won in Won and Below, 1999, Palaeospiculum reedae Won in Won and Below, 1999, and Palaeospiculum devoncourtensis Won in Won and Below, 1999. Micro-computed tomographic (MCT) analysis of Parechidnina aspinosa reveals its skeletal construction through the fusion of unirayed spicules, indicating a close phylogenetic link with archeoentactinids. Blastulospongia bouliaensis n. sp. and Palaeospiculum devoncourtensis represent promising Miaolingian accessory species for biostratigraphy during the Drumian-Guzhangian interval.

UUID: http://zoobank.org/a74cdd4d-6bc3-427b-bf4c-d4f0b79a5c91

The Llandoverian (Telychian) Schoolcraft Formation of Schoolcraft County in the Upper Peninsula of Michigan includes several intervals of exceptional preservation marked by abundant specimens of the noncalcified macroalga Thalassocystis striata Taggart and Parker, 1976. Here, two new noncalcified macroalgal species are described from one of these algal-Lagerstätten intervals. The monopodial thallus of Archaeobatophora gulliverensis new species resembles that of the living dasycladalean green alga Batophora Agardh, 1854 and consists of a cylindrical main axis bearing whorls of branched laterals. It is the second species to be assigned to Archaeobatophora Nitecki, 1976, the type species of which is known only from the Upper Ordovician of neighboring Delta County and the diagnosis of which is emended herein. The thallus of Earltonella swinehartii new species consists of a horizontal stolon that bears a series of upright pinnate fronds. This taxon broadly resembles the living bryopsidalean green alga Caulerpa Lamouroux, 1809 and is the second species to be assigned to Earltonella LoDuca in LoDuca et al., 2023, a genus otherwise known only from approximately age-equivalent strata in the Lake Timiskaming area of Ontario. Additionally, a new Thalassocystis striata occurrence is reported from the Schoolcraft Formation in neighboring Mackinac County, extending eastward the geographic range of this Codium-like bryopsidalean taxon within the Michigan Basin. Viewed in broader terms, the two new species show complex thallus morphologies consistent with a previously documented large-scale morphological pattern in the early Paleozoic evolutionary history of macroalgae and contribute to an emerging understanding of major early Paleozoic radiations of both dasycladalean and bryopsidalean algae that produced, by the mid-Silurian, diverse floras of siphonous green macroalgae broadly similar to those that thrive today in Florida Bay and the Bahama Banks.

We report new interpretation of >19,500 beach strandlines from waterbodies in the western St. Lawrence and Champlain Lowlands in northern New York and adjacent areas of Vermont, Quebec, and Ontario from ≤2-m-resolution digital elevation models. Strandline evidence supports a deglaciation model in which proglacial lake and marine shoreline deposits adjusted continuously in response to steady shoreline regression linked to outlet incision, differential isostatic adjustments, and postglacial relative sea-level rise. Gaps in strandline preservation reflect times of rapid water-level decline associated with breakout floods and abrupt shifts in drainage to new outlets. Water levels returned to slower, steady decline and renewed beach sedimentation during the later stages of a breakout as water levels in the source and receiving waterbodies equilibrated. Our conclusions contrast with previous models that infer discrete lake stages were controlled by stable outlets then fell abruptly as lower outlets were exhumed from beneath the Laurentide Ice Sheet during deglaciation. We present a new deglacial chronology and lake nomenclature that reflects this paradigm and redefines the spatial and temporal distributions of proglacial lake and marine water in the region.

The Guanajuato Mining District of central Mexico is one of the main silver and gold deposits in the world. It is in the State of Guanajuato in the southern part of the Sierra Madre Occidental (SMO) volcanic province. The mining district developed within a mid-Tertiary volcano-sedimentary sequence that includes thick alluvial-fan deposits accumulated in a tectonic basin during the Eocene-Oligocene named the Guanajuato Red Conglomerate and an overlying volcanic sequence mostly pyroclastic of Oligocene age. The mid-Tertiary stratigraphy of Guanajuato is revised and reinterpreted in the light of new fieldwork and U-Pb ages, which document a close timing between all units of the volcanic succession at the top of the Guanajuato Red Conglomerate. This sequence is made of pyroclastic density current deposits formed during episodic events from the Guanajuato caldera. A new nomenclature of the caldera’s units is proposed; the Guanajuato Caldera Volcanic Group, which includes the Guanajuato Pyroclastic Formation represented by the Loseros PDC deposits and the Bufa-Calderones ignimbrites emplaced around 32.8 ± 0.2 Ma, and the post-collapse lava domes of El Rodeo and Chichíndaro formations emplaced at 31–30 Ma. Apparently, a resurgent pulse of the caldera uplifted the collapsed intra-caldera blocks, so that the caldera floor is now exposed. The caldera collapse was controlled by the pre-existing normal faults inherited from the previous tectonic basin; thus, it is classified as a graben-type caldera, with a square shape and a size of 15 × 16 km. By comparison with other similar calderas of Mexico, the Guanajuato caldera is another case study of graben-type calderas of the SMO coinciding with mineral districts, such as Bolaños (Jalisco).

Since the 1990s, Pine Island Glacier (PIG) has been a focal point of research due to its vulnerability within the West Antarctic Ice Sheet. Decades of research have interrogated this dynamic glacier system with a focus on its main trunk and the ice shelf section bordering and stabilizing PIG to the south (the ‘south shelf’), receiving comparatively less attention. Using satellite-derived observations from 2017 to 2023, we document marked dynamic changes on the south shelf, particularly following PIG’s 2018 calving event, which removed >60 km2 of ice from this section. Measurements of surface deformation, ice velocity and strain rates from synthetic aperture radar and optical imagery show localized acceleration and structural weakening of the south shelf near-coincident with this loss. Our findings, highlighting the role of peripheral ice shelves in glacier-system stability, suggest that PIG’s new configuration—characterized by weakening margins and a compromised south shelf—may result in a geometry that grows progressively unstable.

In this study, we established an annually resolved chronology for the upper 98.5 m of a 210.5 m deep ice core (Styx-M core) drilled at the Styx Glacier plateau (SGP) in northern Victoria Land, East Antarctica, to reconstruct the multi-centennial variations of the snow accumulation rate (SAR). The core was dated via the annual layer counting of highly resolved impurities exhibiting seasonal cycles. The layer counting result was constrained using multiple temporal markers, including the 239Pu peaks that resulted from atmospheric weapon tests as well as five large volcanic eruptions in recorded history. These approaches show that the Styx-M core chronology covered 755 years (1259–2014 CE), with the estimated dating uncertainties of ±8 years. The annual accumulation record was derived using the depth-age scale and depth-density relationships of the core. This record revealed a long-term trend of a ∼30% increase in the SARs over the past 755 years, overlapping the pronounced inter-decadal and multi-decadal fluctuations. Further study will be needed to reveal the complex interaction of oceanic and atmospheric processes controlling the temporal fluctuations of SARs in the coastal areas of northern Victoria Land, combining multiple proxy records in the Styx-M core.

Continuous monitoring of the mass balance of the Greenland ice sheet is crucial to assess its contribution to the rise of sea levels. The GRACE and GRACE-FO missions have provided monthly estimates of the Earth’s gravity field since 2002, which have been widely used to estimate monthly mass changes of ice sheets. However, there is an 11 month gap between the two missions. Here, we propose a data-driven approach that combines atmospheric variables from the ERA5 reanalysis with GRACE-derived mass anomalies from previous months to predict mass changes. Using an auto-regressive structure, the model is naturally predictive for shorter times without GRACE/-FO observations. The results show a high r2-score (> 0.73) between model predictions and GRACE/-FO observations. Validating the model’s ability to reproduce mass anomalies when observations are available builds confidence in estimates used to bridge the GRACE and GRACE/-FO gap. Although GRACE and GRACE-FO are treated equally by the model, we see a decrease in model performance for the period covered by GRACE-FO, indicating that they may not be as well-calibrated as previously assumed. Gap predictions align well with mass change estimates derived from other geodetic methods and remain within the uncertainty envelope of the GRACE-FO observations.

The first precise, biostratigraphically bracketed U-Pb dates on the middle Middle Cambrian come from the Rte. 111 ash (new) in the lower Manuels River Formation of southern New Brunswick. Manuels River black mudstone (Avalonian depositional sequence [Ads] 8) unconformably overlies Fossil Brook Member greenish mudstone (Ads 7) of the Chamberlain’s Brook Formation, and the two units should not be combined into a ‘Forest Hills Formation’ (abandoned). This unconformity marks the trans-Avalonian (i.e., Rhode Island–Belgium) green–black boundary and onset of ca. 26 Ma of dysoxic/anoxic marine deposition. Trilobites and agnostids correlate the surprisingly endemic, upper Paradoxides abenacus Zone and Rte. 111 ash into the Hypagnostus parvifrons Zone (Drumian) in Avalonian Wales, Baltic upper ‘Acidusus’ atavus Zone and upper Mawddachites hicksii–lower Paradoxides davidis zones of Avalonian Newfoundland and Britain. The Manuels River Formation in SE Newfoundland and coeval Nant-y-big Formation in South Wales have not yielded ash dates. However, our U-Pb zircon analyses of the Rte. 111 ash in the lower Manuels River in southern New Brunswick yield statistically identical ages of 501.44 ± 0.10 and 501.45 ± 0.08 Ma. The Ads 7–8 unconformity is locally 6–10 m lower in New Brunswick and is somewhat older. Our ages for the Rte. 111 ash show the lower Drumian is significantly younger than previous estimates, is ca. 4.9 Ma younger than the Lower–Middle Cambrian boundary, and debunks claims of a continuous Lower–Middle Cambrian succession in Avalonian New Brunswick where a ca. 7 Ma hiatus is present.

Medusozoa comprise a diverse group of marine invertebrates that includes cubozoans, hydrozoans, staurozoans, and scyphozoans, which play a fundamental role in marine ecosystems. In Cuba, with exceptions, most of the studies of the phylum Cnidaria have focused on the scleractinian corals. However, their close relatives, the jellyfish have been poorly addressed, limiting themselves to isolated records of some species. In this study, we aimed to update the list of medusozoan species registered in Cuba and compare it with the registries in the Greater Caribbean region. Peer-reviewed publications, museum collections, field-trips, global repositories, and social networks were accomplished to compile a species list. Twenty-one new species are recorded, and the distribution of 11 species previously reported is expanded. Cuba, with 361 species is the country with the highest species richness in the Caribbean region: 342 species of Hydrozoa are distributed in 69 families, 16 species of Scyphozoa are distributed in 10 families, and three species of Cubozoa each belong to one family. Analysing the studies of Medusozoa reveals significant heterogeneity in jellyfish species composition across the Caribbean region, where Cuba, Puerto Rico, Mexico, and the USA are the countries with the highest species richness. A high similarity was observed between the assemblages from Cuba and the USA. The number of jellyfish species reported for Cuba constitutes a baseline for ecological studies of their integrated role in marine ecosystems. Studies in the Caribbean region are heterogeneous, with an imbalance in the sampling effort in time and space and probably underestimate the number of species known.